1. Field
Example embodiments relate to a semiconductor memory system, for example, a semiconductor memory system including a volatile memory and a non-volatile memory, which share a common bus, and a method for controlling the operation of the non-volatile memory.
2. Description of the Related Art
Conventional memory systems may independently utilize a volatile memory and a non-volatile memory, where the control of the volatile and non-volatile memory may be performed separately. For example, the volatile memory may require a memory controller, and the non-volatile memory may require another memory controller. However, in order to guarantee high-speed characteristics and reduce the total number of input/output pins required, memory systems having a volatile memory and a non-volatile memory, which share a common bus, have recently been developed.
A conventional non-volatile memory (e.g., NOR flash memory) may require more row addresses than a volatile memory (e.g., dynamic random access memory (DRAM)) in order to select a word line. Therefore, in order to select a word line, the volatile memory may perform an active command only once, but the non-volatile memory may perform the active command twice.
Furthermore, as compared to a conventional volatile memory, the conventional non-volatile memory may utilize a buffer memory when performing a read/write operation on a memory cell array. For example, in order to write data to the non-volatile memory, the data may not be written directly to the non-volatile memory, but rather may be first stored in the buffer memory. Thereafter, if an appropriate amount of data is stored in the buffer memory or a write command is applied to the buffer memory, the stored data may be written to the non-volatile memory cells. Likewise, in order to read data from the flash memory, the data may be first read from the non-volatile memory cells, and then may be temporarily stored in the buffer memory. Thereafter, if an appropriate amount of data is stored in the buffer memory or a read command is applied to the buffer memory, the stored data may be outputted from the non-volatile memory. An operation for reading the data from the non-volatile memory cells and temporarily storing the data in the buffer memory during the read operation may be referred to as a sensing operation.
Generally, a duration of time required to perform the sensing operation after an active command is applied may be referred to as a sensing time. In conventional systems, both the read and write operations have a sensing time. For example, a conventional non-volatile memory may not be able to determine whether to perform the read operation or the write operation when an active command is applied to the non-memory. Because the conventional non-volatile memory cannot make this determination, the non-volatile memory may perform the sensing operation with respect to the read and write operations. Performing the read operation after the sensing time does not pose many problems, but performing the write operation after the sensing time may lead to an unnecessary consumption of current and sensing time.